Eicosanoids are hormones that act as nerve transmitters (neurotransmitters) and modulators of the immune system. These hormones are also involved in inflammatory processes. Overall, the following types of eicosanoids can be distinguished: Prostaglandins comprise a large number of subgroups, for example prostaglandin D2, prostaglandin E2, prostglandin I2 (prostacyclin) or thorboxanes.
- Prostacyclins (part of the prostaglandins)
- Thromboxanes (part of the prostaglandins)
Formation of the eicosanoids: The eicosanoids are formed from the fatty acid arachidonic acid, which is converted to the definitive hormones by enzymes in the following synthesis steps. The enzymes responsible for the formation of hormones include cxclooxygenase (COX, prostaglandins), prostacyclin synthase (prostacyclin), lipoxygenase (leukotrienes) and thromboxane synthase (thromboxanes). Prostaglandin synthesis occurs in many organs, as do prostacyclin and thromboxane formation. Leukotrienes are produced in the white blood cells (leukocytes) and in the macrophages. Each of these hormones has its own receptors.
Regulation of eicosanoids: Prostaglandins, prostacyclins and thromboxanes are released in a tissue-specific manner. For example, they promote inflammation, reduced blood flow (ischemia) or cell damage; glucocorticoids have an inhibitory effect. The most important stimulators of leukotriene release are inflammatory stimuli.
In their function as hormones, eicosanoids have a broad spectrum of action. The individual prostaglandins act partly in opposite directions (antagonistic).